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We employ a novel computational modelling framework to perform high-fidelity direct numerical simulations of aero-structural interactions in bat-inspired membrane wings. The wing of a bat consists of an elastic membrane supported by a highly articulated skeleton, enabling localised control over wing movement and deformation during flight. By modelling these complex deformations, along with realistic wing movements and interactions with the surrounding airflow, we expect to gain new insights into the performance of these unique wings. Our model achieves a high degree of realism by incorporating experimental measurements of the skeleton’s joint movements to guide the fluid–structure interaction simulations. The simulations reveal that different segments of the wing undergo distinct aeroelastic deformations, impacting the flow dynamics and aerodynamic loads. Specifically, the simulations show significant variations in the effectiveness of the wing in generating lift, drag and thrust forces across different segments and regions of the wing. We employ a force partitioning method to analyse the causality of pressure loads over the wing, demonstrating that vortex-induced pressure forces are dominant while added-mass contributions to aerodynamic loads are minimal. This approach also elucidates the role of various flow structures in shaping pressure distributions. Finally, we compare the fully articulated, flexible bat wing with equivalent stiff wings derived from the same kinematics, demonstrating the critical impact of wing articulation and deformation on aerodynamic efficiency. 

Abstract Immersed boundary methods (IBMs) have evolved over the past 50 years from a specialized technique in biofluid dynamics and applied mathematics to a cornerstone of computational fluid dynamics. Many recent advancements in immersed boundary methods have centered on sharp-interface immersed boundary methods, which offer enhanced accuracy and fidelity for flow simulations. This paper outlines the key principles that have driven our own efforts in the development of sharp-interface immersed boundary methods over the past 25 years. We also highlight the power and versatility of these methods by showcasing a range of applications, spanning biolocomotion (i.e., swimming and flying), physiological flows, compressible aerodynamics, fluid–structure interaction (FSI), and flow-induced noise.